1. Field of the Invention
The present invention relates to a device for adding a new function to a computer so as to extend functions of the computer.
2. Description of the Related Art
FIG. 5 is a block diagram showing a skeleton structure of a personal computer.
A configuration of FIG. 5 includes a CPU 1, a PCI bus 2, and an extension device 3. The extension device 3 is connected to the PCI bus 2 for the purpose of extending functions of the personal computer.
The extension device 3 adds functions thereof to the personal computer. When a new function needs to be added to the extension device 3 to create a new extension device having the new function and the existing functions, two different schemes are available to achieve this object. In a first scheme, a new extension device 4 is simply a modified version of the extension device 3 as shown in FIG. 6. In a second scheme, a new extension device 7 is a combination of the old extension device 3 and a new extension device 5 connected together via a PCI bus 6, as shown in FIG. 7.
The extension device 4 of the first scheme is generated by modifying the old extension device 3, so that the extension device 4 has new attribute information 4A assigned thereto. The extension device 7 of the second scheme includes the old extension device 3, so that the new extension device 5 is provided with attribute information 3A of the old extension device 3.
Since the extension device 4 of the first scheme is created by modifying the extension device 3, development of the extension device 4 involves redesigning of a entire device configuration. This results in a lengthy development period.
The extension device 7 of the second scheme is a combination of the old extension device 3 and the new extension device 5, so that the extension device 3 can be used as it is without making any modification to its design. Development of the extension device 7 involves only the development of the new extension device 5, and, thus, can be finished in a shorter time period. The configuration of the second scheme, however, has a drawback as lacking universal applicability in that new functions need to be specially adapted to the old extension device 3.
Accordingly, there is a need for an extension device which can provide both old functions of an old extension device and new functions of a new extension device, and can offer universal applicability while requiring a relatively short time period for design and development.
Accordingly, it is a general object of the present invention to provide an extension device which can satisfy the need as described above.
It is another and more specific object of the present invention to provide an extension device which can provide both old functions of an old extension device and new functions of a new extension device, and can offer universal applicability while requiring a relatively short time period for design and development.
In order to achieve the above objects according to the present invention, a device for extending functions of a computer connected thereto by adding a new function to functions of an existing extension device includes a non-volatile memory that is a rewrite-enable memory, and a new extension device connected to the non-volatile memory and capable of being connected to the computer via a bus and to the existing extension device, said new extension device transferring what is stored in said non-volatile memory to the computer when the computer requests attribute information of the existing extension device.
Since the existing extension device described above can be used without making any modification to its design, development of the whole device involves only the development of the new extension device. This results in the development being completed in a relatively short time period. Further, the device of the present invention is provided with the write-enable memory. When there is a need to replace the existing extension device with another extension device, modifying the attribute information in the write-enable memory is all that is necessary to cope with the new configuration. Therefore, universal applicability is insured.
According to another aspect of the present invention, a device for extending functions of a computer connected thereto by adding a new function to functions of an existing extension device includes a bus capable of having the existing extension device connected thereto, and a new extension device connected to the bus and capable of being connected to the computer via another bus, said new extension device transferring a request for attribute information sent from the computer to said existing extension device, and transferring the attribute information sent from the existing extension device to the computer.
Since the existing extension device described above can be used without making any modification to its design, development of the whole device involves only the development of the new extension device. This results in the development being completed in a relatively short time period. Further, the new extension device issues a request for attribute information to the existing extension device when the host computer requests the attribute information of the existing extension device, and receives the attribute information from the existing extension device to send it to the host computer on behalf of the existing extension device. Because of this configuration, even when another extension device having different attribute information is provided in place of the existing extension device, no design change is necessary in the circuit of the new extension device. Therefore, universal applicability is insured.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.